A radial swivel motor usually consists of a housing, which has at least one stator wing in the interior and is closed on the faces with covers, and of a rotor, which is composed of a driven shaft mounted in the covers and at least one rotor wing. The rotor wing is pivotable against the stator wing of the housing only to a limited extent and thus forms, with the stator wing, at least one pressure chamber and one inlet chamber.
To guarantee the inner tightness between the pressure chamber and the inlet chamber, both the rotor wing and the stator wing are equipped with a form-fitting sliding sealing element, which rests against the lateral covers and against the inner wall of the housing or against the rotor. Again and again, a great number of tightness problems occur right in this area because the sealing elements are subject to increased wear. This is due to the limited rotary motion of the rotor, which changes again and again, and because the sealing elements are also exposed to a very broad operating temperature range.
A few suggestions have already become known for solving these problems. Thus, DE 199 35 234 C1 describes an embodiment of the sliding sealing element, which consists of a filler piece that carries a circular sealing body under pretension, whereby the filler piece is embodied as divided and thus longitudinally mobile parallel to one another, and at least one spring element is arranged between the filler pieces. Thus, the filler pieces are twisted by forces each acting in opposition to one another. The drawback of this sealing variant is that the sealing strip consists of a large number of component parts and thus it is expensive to manufacture and complicated to mount. Moreover, the spring elements consisting of a soft material have only a low volume, so that the pretension forces produced are therefore also very low. What's more, the spring elements only act in the radial direction. All of this leads to leakage.
Supporting the action of an elastic pretension element with one or more metal springs integrated in the pretension element is now known from DE 199 27 619 A1, whereby the metal spring may be a diaphragm spring, corrugated spring, coil spring or compression spring. The pretension forces for the sealing elements are increased by means of the additional metal springs; however, this solution can hardly be technically embodied for this purpose. The compression springs must act, namely, in the radial and axis-parallel directions in relation to the axis of rotation and thus the compression springs must also be arranged in an intersecting manner. This requires a very wide mounting space in the axial direction, which is simply not present because of the dimensions of the rotor wing or of the stator wing.
On the other hand, DE 199 27 621 A1 discloses a strip-like sliding sealing element that consists of a first square sealing frame made of PTFE, a second square sealing frame made of PTFE and a pretension element made of an elastomer. Both sealing frames and the pretension element are designed as being of the same size and are joined together in a sandwich-like manner into a pack by bonding or by vulcanization, and both sealing frames are arranged offset to one another both in the radial and axial directions. The pretension element is arranged between the two sealing frames and, with corresponding lateral projections, engages in the cavities of the two sealing frames, so that the two sealing frames, when installed in the swivel motor, are pretensioned in opposition by the forces of the pretension element equally in the radial and axial directions.
All of the solutions mentioned have in common the fact that the actual sealing element consists of a hard plastic PTFE and is loaded by a corresponding spring element to reduce the sealing gap. This spring element is usually an elastomer material. Sealing elements made of PTFE have good sliding properties, as a result of which they are actually readily suitable for sealing components sliding on one another. However, an open sealing gap, through which compressed oil can overflow, always remains for manufacturing reasons. The size of the sealing gap is, however, also dependent on the operating temperature of the swivel motor. Thus, the sealing gap expands as the temperature becomes lower, while with a higher temperature the contact pressure of the sealing elements at the housing parts increases. With an expanding sealing gap, the waste oil stream increases, and with a higher contact pressure, the wear of the sealing elements increases. Both are unwanted.
All the sliding sealing elements mentioned are thus unsuitable for the required temperature range of −40° C. to 130° C.